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Full text of "The manufacture and properties of iron and steel"

264
METALLURGY OF IRON" AND STEEL.
It is quite evident that the pieces which were heated twice, and which received only one inch of reduction after the second heating, must have heen finished hotter, as well as have received less work after a full heat, hut in spite of these differences in amount of work and temperature it is clear that the bars are practically uniform in strength and ductijity, showing that the steel was in thoroughly good condition originally, and that proper heating did no harm when followed hy a fair amount of work.
The ultimate strength is fairly uniform save in the case of the two hars which were finished at a cherry red heat. The elastic ratio varies in much greater measure, but the results are not regular since, in some cases, as in JT, a high ratio accompanies heavy, reduction under the hammer, while in others, as in D, it appears in bars which have received very little work.
TABLE XIV-F.
Comparative Physical Properties of Test-Pieces of Bessemer Steel •   Cut from Thick and Thin Angles of Large and' Small Sizes.
Each figure is an average of 50 bars.
Thickness of angle ; inches.	Elastic limit: Lbs. per sq. in.		Tilt, strength; Ibs. per sq. in.		Elastic ratio; per cent.		Elongation, in 8 in.; percent.		Reduction of area; per cent.	
	Large sizes.	Small sizes.	Large sizes.	Small sizes.	Large sizes.	Small sizes.	Large sizes.	Small sizes.	Large sizes.	Small sizes.
1	48002 " 48687 41671 41080 40391 88867 ,	44158 43090 43128 41684 41886 40944	60097' 60019 60120 59467 59860 68267	61252 60629 60239 59151 59750 59084	'71.55' 72.70 69.81 69.08 68.04 66.70	72.09 71.07 71.59 70.88 70.02 69,80	'ss.is' 28.16 28.58 28.65 29.03 28.87	27.55 28.55 28.52 29.24 28.74 29.38	'58.23" 57.59 55.17 55.30 58.43 51.68	56.79 54.80 57.58 56.96 57.59 56.07
The original bar A shows a h,igh ratio, but this was finished at a low heat. In the annealed bar B the ratio drops very much, but the "burned" bloom L shows almost as high an elastic strength as the original steel. In the bar M, which shouM. be compared with the bar Q, it is shown that reheating and hammering will do very much, toward' restoring- a piece of burned .steel to its original condition, although it is doubtful whether it ever can make of it a thoroughly relifible material. •                  ' '
SEC.XlVe.—Tests'on Pennsylvania Steel Company angles of different tJiwlcnes'se&.—'ThG 'fact that there is very little difference between thick and thin pieces, provided the work has been sufficient inhpib, cases, is shown by Table XIV-F. Thig was constructed by